类太阳恒星磁场的太阳标度

假定太阳是一颗普通的恒星，对太阳磁场的高分辨率观测，则从内禀磁场强度，尺度谱，面积填充因子，成穴分布趋势，双极分布特征和演化时标等多方面，为类太阳恒星磁场测量提供了一个基本标度，本文综述了与恒星磁场测量有关的，太阳磁场若干观测特征，与类太阳恒星测量结果对比表明，类太阳恒星磁场的内禀强度与太阳磁场接近，但面积填充因子大１－２个数量级，这可能真实地反映了恒星磁场的内禀强度成太阳磁场接近，但面积填充因子     

对研制中国太阳塔的看法

目前,我国太阳物理学家使用的仪器,在口径、成像质量,附属设备等方面大致相当于国外五十年代水平。研制中的太阳磁场望远镜和精细结构望远镜具有较高的设计指标,若它们能研制成功,则可在某些方面将观测提高到七十年代水平。但是,它们的空间分辨力——现代太阳仪器最重要的指标,还很难赶上世界水平。我国拥有若干巡视仪     

太阳表面磁场的分布与演化研究进展

太阳磁场、较差自转和内部对流使得日面磁场与磁活动在很大的时间尺度和空间尺度范围均表现得相当复杂.其中最有名的是太阳活动的11年周期,或22年磁周期.在较小时间尺度上,从几秒到几小时,有时太阳大气中会发生一些壮观的爆发事件,如耀斑、日珥爆发、日冕物质抛射等.所有这些形式的事件都与太阳磁场紧密关联.简单评述了太阳磁场起源与观测方法,重点论述了不同尺度太阳磁场的空间分布与演化,介绍了从太阳磁活动现象统计得到的有关太阳磁场的几个典型特征,同时讨论了进一步研究的方向.     

太阳Stokes光谱望远镜的结构及其数据处理方法

云南天文台的太阳Stokes光谱望远镜是一台通过测量磁敏谱线的Stokes参数I,Q,U和V的轮廓来研究太阳磁场精细结构的光谱型矢量磁场测量仪。它利用4个完整的Stokes轮廓所蕴含的丰富信息,完全确定辐射的偏振状态,从而精确地测定太阳黑子区的矢量磁场。文章首先介绍了该望远镜的结构,进而详细地介绍了该望远镜所测量的偏振光谱资料的处理方法。     

基于尺度不变特征点匹配的太阳磁场图像配准与定位方法

不同太阳观测站间存在观测时间、观测范围、观测设备等差异,为了方便科学研究,有必要找到不同观测站间太阳图像自动配准与定位的方法。提出了基于尺度不变特征点匹配的太阳磁场图像配准与定位方法。首先,对原始图像进行对比度增强、降采样等预处理;其次,采用尺度不变特征检测算法提取两图的尺度不变特征点;然后,寻找同名点的方法对两幅图像特征点进行粗配准和粗定位;最后,基于粗定位区域实现太阳磁场图像的精确配准和定位。开展了不同时段磁场图像的配准和定位实验,对匹配点对数、匹配准确率、匹配误差等参数进行了定量分析,实验结果表明,该方法可以自动、准确、快速地实现太阳磁场图像的配准与定位。     

太阳磁场和宇宙线实验规律初探

本文总结了近20年来太阳磁场、太阳行星际磁场的观测结果,较详细地结出了银河宇宙线在空间分布和随太阳活动变化的时间特性,描绘出一幅比较完整的太阳磁场与宇宙线关系的图像。 对于太阳磁场的研究,得到了一般的结论。给出了宇宙线粒子在太阳系中受太阳磁场调制的四种物理因素。     

太阳耀斑的光球磁场和色球速度场观测

太阳磁场望远镜安装了CCD图象接收处理系统后,得到许多精细结构的两维、实时磁场、速度场图。本文对其中观测的两群黑子,做耀斑磁场、速度场分析。在此基础上指出,异极性磁区相互渗透是普遍存在的,耀斑亮核均发生在异极性磁区相互挤压的前锋。这就为挤压无力场耀斑模式提供了有力的证据。同时发现,在耀斑发生的区域,流场的方向是向下的。     

太阳磁场观测研究

简要回顾了近几年国际上太阳磁场研究的一些重要进展，包括耀斑与磁切和电流的关系，电流螺度和磁螺度，磁场拓扑性，三维磁场外推，色球磁场研究，日冕磁场研究，内网络磁元，磁流和振荡，极区磁场观测以及色球磁元观测等方面内容，同时也介绍了怀柔太阳观测站最近所取得的主要成果，自20世纪90年代以来，YOHKOH高分辨率的太阳X射线数据，SOHO的多波段大尺度观测，TRACE的高分辨太阳过渡区资料，为研究太阳磁场从内部到距离几十太阳半径处的大范围演化提供了依据，高效的空间资料结合长期的地面资料，将是正派推动太阳磁场研究的重要手段和必然趋势。     

两个太阳活动区中纵向磁场的分形特征

本研究了１９９０年３月２５日活动区ＡＲ５９８８和１９９０年８月３０日活动区ＡＲ６２３３中太阳磁场的分形特征，主要结果如下：（１）两个活动区中的纵向磁场分布不满足分形布朗曲面；（２）两个活动区中磁场的分形特征十分不同；（３）描述两个活动区磁场分形特征的四个统计参量随时间演化，本扼要讨论了这些结果的物理意义。     

两个太阳活动区中纵向磁场的分形特征(英文)

本文研究了1990年3月25日活动区AR5988和1990年8月30日活动区AR6233中太阳磁场的分形特征．主要结果如下：（1）两个活动区中的纵向磁场分布不满足分形布朗曲面；（2）两个活动区中磁场的分形特征十分不同；（3）描述这两个活动区磁场分形特征的四个统计参置随时间演化，本文扼要讨论了这些结果的物理意义。     

太阳耀斑区磁场和电流研究的一些新进展

在太阳耀斑区磁场和电流研究方面，文中将着重介绍太阳横向磁场方位的确定，太阳活动区磁场的非热性表示、太阳耀斑前后的活动区磁场变化、以及耀斑核块与活动区纵向电流密度极大点位置的关系等几个重要问题的研究现状。     

太阳大气中的光球亮点

首先是对太阳光球亮点近年来研究工作的总结。光球亮点是一种发生在太阳光球上宁静区域的的小尺度和短寿命增亮现象,平均直径在100～300knm之间,平均寿命约为几分钟。光球亮点的研究对于光球辐射和磁场性质的认识具有重要意义。过去的观测显示,绝大多数光球亮点的产生和演化与磁场,特别是光球上的小尺度磁场的演化密切相关,比如,两个同极性磁场的合并,或者反极性磁场的对消,或者一个同极性磁场的分裂,均可以促使光球亮点产生或消失。基于这样的观测结果,统计研究了2722个光球亮点(1600A)与光球上偶极磁元的关系,发现大约有1/3的光球亮点出现在偶极磁元中心附近。     

太阳大气磁精细结构的射电探讨

太阳大气磁场的研究对于太阳大气物理及太阳活动研究是十分重要的。目前探测光球以外的日够以球，过渡区磁场的几乎唯一办法，是在紧密联系其他频说段取得的信息基础上使用射电观测。根据在微波，米波段有关辐射机制和传播过程，介绍了推导磁场讯息的基本射电方法。     

Dependence of Supergranular Length-Scales on Network Magnetic Fields

In an earlier paper by Raju, Srikanth, and Singh (1998), the average size of chromospheric network cells has been shown to have a dependence on the solar latitude. This was presumed to be due to the reduction of supergranular length-scales by network magnetic field enhancements. It has been found that the network brightness enhancements over solar latitude support this finding. Significant negative correlations have been found between the average cell size and the network brightness enhancements. Since the brightness enhancements are essentially due to the magnetic field concentrations, it is suggested that the network magnetic fields reduce the network cell sizes. We have also obtained the variations of skewness of network brightness distributions over solar latitude, which follow the network field variations. This complements the findings of Caccin et al. (1998) that skewness of brightness distribution follows the solar cycle. The findings suggest that the dependence of supergranular sizes, network brightness, and skewness of network brightness distribution on solar latitude or on the phase of the solar cycle is due to the associated variation of network magnetic fields.     

Fractal properties of solar magnetic fields

We study the spatial properties of solar magnetic fields using data from the Solar Vector Magnetograph of the Marshall Space Flight Center (MSFC) (FeI 5250.2 Å) and SOHO/MDI longitudinal magnetic field measurements (Ni 6767.8 Å) (96-min full-disk maps). Our study is focused on two objects: the fractal properties of sunspots and the fractal properties of the spatial magnetic field distribution of active and quiet regions considered as global structures. To study the spatial structure of sunspots, we use a well-known method of determining the fractal dimension based on an analysis of the perimeter—area relation. To analyze the fractal properties of the spatial magnetic field distribution over the solar surface, we use a technique developed by Higuchi. We have revealed the existence of three families of self-similar contours corresponding to the sunspot umbra, penumbra, and adjacent photosphere. The fractal coefficient has maxima near the umbra—penumbra and penumbra—photosphere boundaries. The fractal dependences of the longitudinal and transverse magnetic field distributions are similar, but the fractal numbers themselves for the transverse fields are larger than those for the longitudinal fields approximately by a factor of 1.5. The fractal numbers decrease with increasing mean magnetic field strength, implying that the magnetic field distribution is more regular in active regions.     

Small-scale magnetic structures on the Sun

Summary The Sun provides us with a unique astrophysics laboratory for exploring the fundamental processes of interaction between a turbulent, gravitationally stratified plasma and magnetic fields. Although the magnetic structures and their evolution can be observed in considerable detail through the use of the Zeeman effect in photospheric spectral lines, a major obstacle has been that all magnetic structures on the Sun, excluding sunspots, are smaller than what can be resolved by present-day instruments. This has led to the development of indirect, spectral techniques (combinations of two or more polarized spectral lines), which overcome the resolution obstacle and have revealed unexpected properties of the small-scale magnetic structures. Indirect empirical and theoretical estimates of the sizes of the flux elements indicate that they may be within reach of planned new telescopes, and that we are on the verge of a unified understanding of the diverse phenomena of solar and stellar activity.In the present review we describe the observational properties of the smallscale field structures (while indicating the diagnostic methods used), and relate these properties to the theoretical concepts of formation, equilibrium structure, and origin of the surface magnetic flux.On leave from Institute of Astronomy, ETH-Zentrum, CH-8092 Zürich, SwitzerlandThe National Center for Atmospheric Research is sponsored by the National Science Foundation     

How to drive roAp stars

Rapidly oscillating Ap stars constitute a unique class of pulsators with which to study non-radial oscillations under some — even for stars — unusual physical conditions. These stars are chemically peculiar, they have strong magnetic fields and they often pulsate in several high-order acoustic modes simultaneously. We discuss here an excitation mechanism for short-period oscillation modes based on the classical κ mechanism. We particularly stress the conditions that must be fulfilled for successful driving. Specifically, we discuss the roles of the chemical peculiarity and strong magnetic field on the oscillation modes and what separates these pulsators from δ Scuti and Am-type stars.     

Formation of buoyant magnetic structures by a localized velocity shear

Motivated by considerations of the solar tachocline, we study the generation of strong buoyant magnetic structures by a sheared velocity field localized in a convectively stable background, using non-linear three-dimensional (3D) magnetohydrodynamic (MHD) simulations. The shear flow can spontaneously create strong tube-like toroidal (streamwise) magnetic structures from an imposed weak uniform poloidal (cross-stream) magnetic field. The structures are magnetically buoyant and therefore rise, and may evolve further to a rich variety of geometries, including kinked or arched shapes. The emergence process can repeat indefinitely with a characteristic period. These mechanisms may be relevant to the MHD processes in the solar tachocline and the creation and emergence of solar active regions.     

Differential rotation of solar magnetic fields

The connection of the differential rotation of solar magnetic fields with the field sign and strength is studied. The synoptic maps of magnetic fields over the last three solar cycles taken at the Kitt Peak Observatory served as input data for the study. The algorithm of magnetic field filtering over 14 chosen strengt intervals and successive 5-degree latitude zones was applied to these data. The Fourier transform of the time series obtained was then used. Analysis of the power spectra led to the conclusion that there are two types of magnetic fields. These differ in strength (0–50 and 50–700 G) and rotation characteristics. The rotation differentiality for strong magnetic field is almost twice as large as that for weak magnetic fields.     

To the problem of solar coronal heating

We consider the adequacy of various solar coronal heating models. We show that the correlation between the intensity of the coronal Fe XIV 530.5 nm green line and the calculated magnetic field strength in the solar corona can be a useful tool for this purpose. We have established this correlation for coronal structures and magnetic fields of large spatial and temporal scales. The correlation found exhibits a strong dependence on both solar cycle phase and heliolatitude. The efficiency of a particular coronal heating mechanism is probably determined by the relative area occupied by low and high loops (including open structures). The direct current models based on slow field dissipation (DC) and the wave models based on Alfvén and magnetosonic wave dissipation (AC) are more efficient in the equatorial and polar zones, respectively.